In the 3GPPP (3rd Generation Partnership Project), the W-CDMA (Wideband Code Division Multiple Access) system has been standardized as the third generation cellular mobile communication system so as to sequentially launch services. In addition, the HSDPA (High Speed Downlink Packet Access) system has been standardized so as to launch services.
The 3GPP is considering the evolution of third-generation radio accessing (EUTRA: Evolved Universal Terrestrial Radio Access). It proposes the OFDM (Orthogonal Frequency Division Multiplexing) system as the downlink of EUTRA. It also proposes a single carrier communication system based on the DFT (Discrete Fourier Transform)-spread OFDM system as the uplink of EUTRA.
FIG. 9 is an illustration showing uplink and downlink channel configurations for EUTRA. A base station device (BS) transmits data to mobile station devices (MS1, MS2, MS3, etc.) by use of downlinks. The mobile station devices (MS1, MS2, MS3, etc.) transmit data to the base station device (BS) by use of uplinks.
The downlink of EUTRA include a downlink pilot channel (DPiCH: Downlink Pilot Channel), a downlink synchronization channel (DSCH: Downlink Synchronization Channel), a downlink control channel (PDCCH: Physical Downlink Control Channel), a common control channel (CCPCH: Common Control Physical Channel), and a downlink shared channel (PDSCH: Physical Downlink Shared Channel).
The uplink of EUTRA include an uplink shared channel (PUSCH: Physical Uplink Shared Channel), an uplink control channel (PUCCH: Physical Uplink Control Channel), a random access channel (RACH: Random Access Channel), and an uplink pilot channel (UPiCH: Uplink Pilot Channel) (see Non-Patent Documents 1, 2).
FIG. 10 is a chart showing an example of an uplink radio resource configuration. In FIG. 10, the horizontal axis represents time, and the vertical axis represents frequency. FIG. 10 shows the configuration of a single radio frame, which is divided into a plurality of resource blocks. In FIG. 10, resource blocks are configured in units of regions each circumscribed with 1.25 MHz frequency-width and 1 ms time-width, so that the random access channel (RACH), the uplink shared channel (PUSCH), and the uplink control channel (PUCCH) illustrated in FIG. 9 are assigned to these regions.
That is, the random access channels (RACH) are assigned to resource blocks illustrated as dot-hatching regions; the uplink shared channels (PUSCH) are assigned to resource blocks illustrated as blank regions; and the uplink control channels (PUCCH) are assigned to resource blocks illustrated as horizontal-line-hatching regions.
The random access channel (RACH) for the uplink of EUTRA includes asynchronous random access channels and synchronous random access channels. The asynchronous random access channel uses a minimum unit at a 1.25 MHz band. The base station device employs a plurality of random access channels to cope with accesses from numerous mobile station devices. The maximum object of using the asynchronous random access channel is to establish synchronization between the mobile station device and the base station device. The random access channel plays an additional role for issuing a scheduling request which is used by the mobile station device requesting a new uplink resource due to a shortage of assignment of resources (see Non-Patent Document 2).
Asynchronous random access includes two accesses, namely, a contended random access (or a contention-based random access) and a non-contended random access (or a non-contention-based random access).
The contended random access is a normally processed random access likely causing the contention between mobile station devices.
The non-contended random access is a random access causing no contention between base station devices, which is processed under the initiative of the base station device in case of handover or the like for rapidly establishing synchronization between the base station device and the mobile station device.
In asynchronous random access, the mobile station device transmits a preamble for establishing synchronization with the base station device. This is called a random access preamble. This preamble includes signatures, i.e. signal patterns representative of the information. A desired signature is selected from among several tens of preset signatures so as to designate the information consisting of several bits.
In recent EUTRA, the mobile station device transmits 6-bit information to the base station device by way of the signature. The 6-bit transmission needs sixty-four types of preambles, i.e. 2 to the 6th power. The 6-bit information is referred to as a preamble ID. In the 6-bit preamble ID, a random ID is assigned to five bits, while the information representing the amount of information needed for a random access request is assigned to the remaining one bit (see Non-Patent Document 3).
FIG. 11 is a sequence diagram showing a contended random access process for asynchronous random access. First, the mobile station device selects a signature based on various pieces of information such as the random ID and the downlink path-loss/CQI (Channel Quality Indicator), thus transmitting an random access preamble as a message M1 via an asynchronous random access channel (step S01).
Upon reception of the random access preamble from the mobile station device, the base station device calculates a synchronous timing deviation occurring between the mobile station device and the base station device on the basis of the random access preamble, thus, producing the synchronous timing deviation information; it performs scheduling to transmit an L2/L3 (Layer 2/Layer 3) message, thus producing the scheduling information; then, it assigns the temporary intra-cell identification information of the mobile station device (or T-C-RNTI: Temporary Cell-Radio Network Temporary Identity) to the mobile station device.
The base station device sets RA-RNTI (Random Access-Radio Network Temporary Identity), representing that a random access response to the mobile station device transmitting the random access preamble via the random access channel is set to the downlink shared channel (PDSCH), to the downlink control channel (PDCCH).
With the resource block for the downlink shared channel (PDSCH) notifying the allocation of the random access response via the RA-RNTI, the base station device transmits a message M2 representative of the random access response including the synchronous timing deviation information, the scheduling information, the T-C-RNTI and the received preamble ID number (or the random ID) to the base station device (step S02).
The RA-RNTI indicates a specific value which is not used as the C-RNTI (Cell-Radio Network Temporary Identity), so that the mobile station device detects the specific value to identify setting the random access response to the downlink shared channel (PDSCH).
FIG. 12 shows an example of allocation of the random access response to the downlink shared channel (PDSCH) when notifying the mobile station device of the allocation via the RA-RNTI. As illustrated in FIG. 11, in which the allocation of the random access response is notified using the RA-RNTI, the random access response including the synchronous timing deviation information, the scheduling information, the T-C-RNTI and the signature ID number of the received preamble are stored in a single resource block of the downlink shared channel (PDSCH) with respect to a plurality of mobile station devices (i.e. n devices where n is an integer of two or more in FIG. 12).
In FIG. 11, when the mobile station device identifies that the RA-RNTI is set to the downlink control channel (PDCCH) of the message M2, it assesses the content of the random access response set to the downlink shared channel (PDSCH) so as to extract the response including the signature ID number (or the random ID) of the transmitted preamble, thus correcting the synchronous timing deviation based on the synchronous timing deviation information within the response.
Based on the received scheduling information, the mobile station device transmits a message M3 representative of the L2/L3 message including at least the C-RNTI (or the core network ID such as the TMSI (Temporary Mobile Subscriber Identity)) in the scheduled resource block to the base station device (step S03).
Upon reception of the L2/L3 message from the mobile station device, the base station device refers to the C-RNTI (or the core network ID such as TMSI) included in the received L2/L3 message so as to transmit a message M4 representative of a contention resolution identifying the contention occurring between mobile station devices to the mobile station device (step S04). The procedures of steps S01 to S04 are described in Non-Patent Document 3.
FIG. 13 is a sequence diagram showing a transmission process of downlink data from the base station device to the mobile station device according to the conventional technology. The process of FIG. 13 uses HARQ (Hybrid Automatic Repeat Request).
In the process of HARQ, the base station device transmits downlink control data to the mobile station device via the downlink control channel (PDCCH) (step S11).
Then, the mobile station device makes a decision whether or not to detect the downlink control data being transmitted in step S11 (step S12).
The base station device transmits downlink transmission data to the mobile station device via the downlink shared channel (PDSCH) (step S13).
Then, the mobile station device makes a decision whether or not to detect the downlink transmission data being transmitted in step S13 (step S14).
After decoding the data transmitted in step S11 and in step S13, the mobile station device feeds back ACK (Positive Acknowledgement) in the case of a success of CRC (Cyclic Redundancy Check) or NACK (Negative Acknowledgement) in the case of a failure of CRC to the base station device (step S15), thus making a determination whether or not to repeat transmission.
Just after reception of data via the downlink shared channel (PDSCH) in step S13, the ACK/NACK is transmitted via the uplink shared control channel (PUCCH).
Non-Patent Document 1: 3GPP TS (Technical Specification) 36.211, V1.10 (2007-05), Technical Specification Group Radio Access Network, Physical Channel and Modulation (Release 8)
Non-Patent Document 2: 3GPP TS (Technical Specification) 36.212, V1.20 (2007-05), Technical Specification Group Radio Access Network, Multiplexing and Channel Coding (Release 8)                Non-Patent Document 3: R2-072338 “Update on Mobility, Security, Random Access Procedure, etc.” 3GPP TSG RAN WG2 Meeting #58 Kobe, Japan, 7-11 May, 2007        